<title> 能量项链</title><link href="http://hzoi.com/tomorrow.css" rel="stylesheet"><div class="ui existing segment"><pre><code><span class="pl-cp">#include</span> <span class="pl-cpf">&lt;iostream&gt;</span><span class="pl-cp"></span>
<span class="pl-k">using</span> <span class="pl-k">namespace</span> <span class="pl-n">std</span><span class="pl-p">;</span>
<span class="pl-kt">int</span> <span class="pl-nf">main</span><span class="pl-p">()</span> <span class="pl-p">{</span>
    <span class="pl-kt">int</span> <span class="pl-n">n</span><span class="pl-p">;</span>
    <span class="pl-n">cin</span> <span class="pl-o">&gt;&gt;</span> <span class="pl-n">n</span><span class="pl-p">;</span>
    <span class="pl-kt">int</span> <span class="pl-n">a</span><span class="pl-p">[</span><span class="pl-mi">2005</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-p">{</span><span class="pl-mi">0</span><span class="pl-p">};</span>
    <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">i</span> <span class="pl-o">=</span> <span class="pl-mi">1</span><span class="pl-p">;</span> <span class="pl-n">i</span> <span class="pl-o">&lt;=</span> <span class="pl-n">n</span><span class="pl-p">;</span> <span class="pl-n">i</span><span class="pl-o">++</span><span class="pl-p">)</span> <span class="pl-p">{</span>
        <span class="pl-n">cin</span> <span class="pl-o">&gt;&gt;</span> <span class="pl-n">a</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">];</span>
        <span class="pl-n">a</span><span class="pl-p">[</span><span class="pl-n">i</span> <span class="pl-o">+</span> <span class="pl-n">n</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-n">a</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">];</span>
    <span class="pl-p">}</span>
    <span class="pl-kt">int</span> <span class="pl-n">dp</span><span class="pl-p">[</span><span class="pl-mi">200</span><span class="pl-p">][</span><span class="pl-mi">200</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-p">{</span><span class="pl-mi">0</span><span class="pl-p">};</span>
    <span class="pl-kt">int</span> <span class="pl-n">maxnum</span> <span class="pl-o">=</span> <span class="pl-mi">0</span><span class="pl-p">;</span>
    <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">i</span> <span class="pl-o">=</span> <span class="pl-mi">3</span><span class="pl-p">;</span> <span class="pl-n">i</span> <span class="pl-o">&lt;=</span> <span class="pl-mi">2</span> <span class="pl-o">*</span> <span class="pl-n">n</span><span class="pl-p">;</span> <span class="pl-n">i</span><span class="pl-o">++</span><span class="pl-p">)</span> <span class="pl-p">{</span>
        <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">j</span> <span class="pl-o">=</span> <span class="pl-n">i</span> <span class="pl-o">-</span> <span class="pl-mi">2</span><span class="pl-p">;</span> <span class="pl-n">j</span> <span class="pl-o">&gt;=</span> <span class="pl-n">max</span><span class="pl-p">(</span><span class="pl-mi">1</span><span class="pl-p">,</span> <span class="pl-n">i</span> <span class="pl-o">-</span> <span class="pl-n">n</span><span class="pl-p">);</span> <span class="pl-n">j</span><span class="pl-o">--</span><span class="pl-p">)</span> <span class="pl-p">{</span>
            <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">k</span> <span class="pl-o">=</span> <span class="pl-n">j</span> <span class="pl-o">+</span> <span class="pl-mi">1</span><span class="pl-p">;</span> <span class="pl-n">k</span> <span class="pl-o">&lt;</span> <span class="pl-n">i</span><span class="pl-p">;</span> <span class="pl-n">k</span><span class="pl-o">++</span><span class="pl-p">)</span> <span class="pl-p">{</span>
                <span class="pl-n">dp</span><span class="pl-p">[</span><span class="pl-n">j</span><span class="pl-p">][</span><span class="pl-n">i</span><span class="pl-p">]</span> <span class="pl-o">=</span>
                    <span class="pl-n">max</span><span class="pl-p">(</span><span class="pl-n">dp</span><span class="pl-p">[</span><span class="pl-n">j</span><span class="pl-p">][</span><span class="pl-n">i</span><span class="pl-p">],</span> <span class="pl-n">dp</span><span class="pl-p">[</span><span class="pl-n">j</span><span class="pl-p">][</span><span class="pl-n">k</span><span class="pl-p">]</span> <span class="pl-o">+</span> <span class="pl-n">dp</span><span class="pl-p">[</span><span class="pl-n">k</span><span class="pl-p">][</span><span class="pl-n">i</span><span class="pl-p">]</span> <span class="pl-o">+</span> <span class="pl-n">a</span><span class="pl-p">[</span><span class="pl-n">j</span><span class="pl-p">]</span> <span class="pl-o">*</span> <span class="pl-n">a</span><span class="pl-p">[</span><span class="pl-n">k</span><span class="pl-p">]</span> <span class="pl-o">*</span> <span class="pl-n">a</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]);</span>
                <span class="pl-n">maxnum</span> <span class="pl-o">=</span> <span class="pl-n">max</span><span class="pl-p">(</span><span class="pl-n">maxnum</span><span class="pl-p">,</span> <span class="pl-n">dp</span><span class="pl-p">[</span><span class="pl-n">j</span><span class="pl-p">][</span><span class="pl-n">i</span><span class="pl-p">]);</span>
            <span class="pl-p">}</span>
        <span class="pl-p">}</span>
    <span class="pl-p">}</span>
    <span class="pl-n">cout</span> <span class="pl-o">&lt;&lt;</span> <span class="pl-n">maxnum</span> <span class="pl-o">&lt;&lt;</span> <span class="pl-n">endl</span><span class="pl-p">;</span>
    <span class="pl-k">return</span> <span class="pl-mi">0</span><span class="pl-p">;</span>
<span class="pl-p">}</span>
</cpde></pre></div>